I have an archive of all my email going back to 1992. (Granted, this is more accessible prior to 2000 or so when things went unnecessarily to HTML). It is a wonderful resource, not only for practical reasons but also it's like my own personal Pepys diary -- I can tell you what I was doing in 1992 and later on any date. I love reading it, even if I encounter sad messages from mentors who have since passed or significant others decades since the breakup.